Copper sweetening of cracked naphthas and stabilizing the sweetened naphtha with an amine



Oct. 30, 1956 M. KALINOWSKI ETAL 2,768,885 COPPER SWEETENING oF CRACKEDNAPHTHAS AND STABILIZING THE SWEETENED NAPHTHA WITH AN AMINE:

Filed Aug. 27, 1953 /R NN IIIIII INVENToRs Maf/mr l.. Kali/forst! Rober!F. .Sc/unifi:

United States Patent O COPPER SWEETENING OF CRACKED NAPHTHAS ANDSTABILIZING THE SWEETENED NAPH- THA WITH AN AMINE Mathew'L. Kalinowski,Chicago, Ill., and Robert F. Schnalth, Hammond, Ind., assignors toStandard Oil Company, Chicago, Ill., a corporation of IndianaApplication August 27, 19513, Serial No. 376,906.

4 Claims. (Cl. 44--74)` This invention relates to the sweetening ofcracked naphthas which contain objectionable amounts of mercaptans. Moreparticularly, it relates to the sweetening of sour cracked naphthas bymeans of a supported cupric chloride catalyst.

The sweetening of naphthas which contain objectionable amounts ofmercaptans, i. e., commonly known as sour naphthas by treatment with asupported CuClz catalyst is of considerable commercial importance.Probably the best known copper sweetening process is the so-called Lindeslurry process. In this process a catalyst comprising essentially CuCl2,water and a carrier in the form of free ilowing granules is dispersedinto the sour naphtha and the dispersion is maintained until asubstantially sweet naphtha has been obtained whereupon the sweetproduct naphtha is separated from the catalyst. Normally the contactingis carried out in the presence of free-oxygenv in an amount sufficientto regenerate the catalyst. The carrier may be either anadsorbentmaterial such as fullers earth or acid treated clay or anessentially non-adsorbent material such as pumice or diatomaceous earth.The adsorbent materials, preferably linely divided fullers earth, arecommonly used in commercial operation.

The slurry process works very well when treating virgin sour naphthas,The oxidation stability of the sweet virgin naphtha as measured by theASTM induction period method is excellent even in the absence of metalde? activator. However, the solid copper chloride process cannot be usedon sour cracked naphthas because, at the same conditions used for virginnaphthas, the sweet nalphtha has unsatisfactory oxidation stability andpoorer co or.

It is an object of this invention to sweeten sour cracked naphthas usinga supported CuClz catalyst. Another object is a copper chloridesweetening process for sweet ening sour cracked naphthas, whereas thesweet naphtha has an acceptable oxidation stability as measured by theinduction period method. Other objects will become apparent in thecourse of the detailed description.

A sweet cracked naphtha of improved oxidation stability is obtained bycontacting a sour cracked naphtha, in the presence o-f free-oxygen, at atemperature below about 120 F., preferably about 70-90 F., with asupported copper chloride sweetening catalyst wherein the weight ratioof carrier to CuClz is about :1 or more, for example, 12:1. It ispreferred to add to the sweet naphtha an effective amount of anoxidation inhibitor and a metal deactivator.

The invention is described in relation to the annexed figure which formsa part of this specification. The gure shows one illustrative embodimentof the process of this invention. equipment have been omitted from theembodiment shown in the ligure; these items may be readily added bythose skilled in the art.

The feed stock to the process is a sour naphtha derived from the thermalor catalytic cracking of gas oils, reduced crudes and heavy naphthas.The feed may consist of a Numerous pumps, valves and other items of2,768,885 Patented oct. 3o, `1956 ICC mixture of cracked naphtha andVirgin naphtha wherein the cracked naphtha is the predominant component.The feed may be a cracked naphtha which has been subjected to priortreatment for reduction in mercaptan content or sulfur content, e. g.,the efluent'from the treatment of a sour cracked naphtha by one of thewell known solutizer processes, which efuent is sour to the doctor testeven though said eiiiuent has a copper number of 2 or 3. The sour oillshould be HzS-free. lf the feed contains H25, the HzS should be removedby washing with a dilute aqueous caustic solution or other method ofremoving HzS that does not also remove all the mercaptans.

Caustic solution reacts with the copper catalyst and deactivates it.Therefore, it is necessary to remove any caustic which may be present inthe feed. The sour oil feed in this illustration, a naphtha derived fromthe thermal cracking of a virgin gas oil which has a mercaptan No. of 5and an ASTM boiling range from 130 to 400 F., is passed from source 1lthrough line 12, into salt filter 13. Salt filter 13 consists of acylindrical vessel filled with crushed rock salt. The rock salt removesany aqueous caustic that may be occluded in the feed. Instead of using asalt drum, a vessel filled with steel wool, gravel, sand or othercoalescing medium may be used.

The naphtha is passed from salt filter 13 by way of line 14, into heatexchanger 16. In heat exchanger 16 the temperature of the sour crackedoil is raised to about 80 F. Although the temperature of operation maybe as high as about 120 F., better results are obtained by operatingbelow about 90 F. From heat exchanger 16 n theoil is passed by way ofline 17 into mixer 18. Mixer In general, from about 3 to about 9standard cubic feet of free-oxygen or an equivalent amount of air areused in the process per pound of mercaptan sulfur. Herein 4.5 s. c. f.of free-oxygen are used.

A side stream of the sour cracked naphtha is withdrawn from line 17 byway of line 24 and isr passed into slurry tank 26. Slurry tank 26 is acone-bottomed vessel provided with an agitator not shown. Fresh catalystfrom source 27 is added by way of line 28 to slurry tank 26. The slurryof catalyst and sour cracked naphtha is passed from tank 26 through line28 by way of pump 31 into line 32. The main stream of sour crackednaphtha is passed from mixer 1S by way of line 34 and pump 36 into line37 where it meets the makeup catalyst slurry from line 32.'

The catalyst comprises essentially CuClz, water and a carrier. `Herein,the carrier consists essentially of a finely powdered mixture, having ascreen size of less than about mesh of Attapulgus clay. Adsorbed on thecarrier is an aqueous solution of CuCl2, Based on the total catalyst,the catalyst should contain between about 5 and 30 weight percent ofwater. A water content of 15 to 25% is preferred to minimize catalystcarryover.

The CuCl2 may be added by using either the anhydrous salt. Or, the CuClzmay be made by reacting in aqueous solution cupric sulfate and sodiumchloride or ammonium chloride. When forming the CuClz by this reaction,it is preferred to use a small excess of the chloride salt. The weightratio of carrier to CuClz must be at least about 10:1 and may be as highas 20:1. It is preferred to use a ratio between about 12:1 and 15:1.

In this illustration the Attapulgus clay to CuClz weight ratio is 13:1land the total catalyst mass contains 20 weight percent of water. Thenaphtha-oxygen-catalyst dispersion in line 37 is passed into eductor 33and from eductor 38 it is passed through line 39 into reactor 41. Insome cases the edutor may be by-passed and the dispersion passed into'line 39 by way of by-pass line 42. I-n reactor 41 the naphtha and thecatalyst `are maintained in the dispersed condition until the nap'hthais substantially sweet.

Reactor 41 has a conical shaped lower portion into which the catalystsettles. The dense slurry of catalyst and napht-ha is withdrawn from thebottom of reactor 41 through line 46 and lis passed into eductor 3S byway of line 47. ln `eductor 38 the recycle catalyst meets the stream orsour naphtha and makeup catalyst. Catalyst circulation rate may bebetween about l and 30 volume percent, based on naphtha; rates betweenand 20% are preferred to reduce carryover. When the catalyst has become`substantially inactive, catalyst is sent to recovery by way of lines 46Iand 49.

The sweet naphtha usually contains a very slight amount of catalyst(carryover). The copper in the catalyst has an `adverse eiect on theoxidation and color stability of the naphtha. The catalyst-containingsweet naphtha is withdrawn from reactor 41 through line 51 yand ispassed into line 52 where it meets water from `source S3 in line 54. rheyamount of lwash water used is dependent upon the amount of catalystcarried over from the reactor. In general the amount of wash Water maybe between about 10 and 100 volume percent based on sweet naphtha. Themixed stream of water and sweet naphtha is passed into mixer 56. Frommixer 56 the stream of sweet naphtha and water is passed by way of line57 into `settler 58. The wash water separates in settler 58 Land is sentto a sewer by way of line 59. The washed sweet naphtha from settler 58is passed into line 61. The washing operation may be by-passed by way oflines 51 and 62. The washed naphtha from line 61 is passed through line63, through cooler 64 and line 66 into salt iilter 67. Cooler 64 lowersthe temperature of the washed naphtha in order to reduce the amount ofwater dissolved in the naphth-a, and salt filter 67 dehydrates thewashed naphtha. Brine from vessel 67 is passed to the sewer by way ofline 68. Salt lilter 67 is similar in construction to salt filter 13.

Sweet naphtha is Withdrawn from the filter by way of line 69. A solutionof phenylene diamine-type inhibitor and copper metal deactivator fromsource 71 is introduced by way of line 72 into line 69. The PDA-MDsolution and the sweet naphtha are intermingled in mixer '73. Thestabilized naphtha is passed to product storage by way of line 74.

The phenylene diamine inhibitors may be N,Ndi alkyl-p-phenylene diaminesin which the alkyl groups contain from 1 to about l2 carbon atoms permolecule including such compounds as N,Ndiisopropylp phenylene diamine,N,N-diamylpphenylene diamine, N,Nd.ihexylp-phenylene diamine, etc., aswell as Ithose in which the alkyl groups are dieren't as, for example,in such compounds as Npropyl-N-butylp-phenylene diamine,N-butyl-N-amylp-pheny1ene diamine, N-hexyl- N'octyl-pphenylene diamine,etc. Generally between about 0.5 and l0 pounds of inhibitor are used per1000 barrels (42 gals.) of oil. Herein, 1 lb./M. bbls. (42) ofN,N-di-secabutyl-pphenylene diamine is used.

It is to be understood that other types of oxidation inhibitors may beused, e. g., butylcatech ol.

The metal deactivator may be any one of the classes of compounds set outin Ind. and Eng. Chem. 41, 918 (May 1949). Usually between about 0.5 andl0 pounds of metal deactivator per 1000 barrels (42 gals.) of oil areused. Herein, 2 lbs/M bbls. (42) ofN,N-disalicylidine-l,Z-diamino-propane are added.

It is to be understood that the vabove-described embodiment isillustrative only and is not intended to 'limit the scope of thisinvention. :Many variations thereon can be readily made by those skilledin the art.

In order to illustrate the results obtainable with this invention, testswere made on la thermally cracked sour naphtha having a mercaptan numberof 5 and a boiling range between 130 and 400 F. These tests were carriedout in a laboratory size continuous pilot plant which closely simulatesthe operation of a l-arge scale commerical unit. In eaoh run 6 liters ofsour cracked naphtha were passed 'through the apparatus.

The catalyst consisted of CuClz, water and Attapulgus clay finescarrier. lhe catalyst masswas prepared using hydrated cupric chloride,i. e., CuCl2-2H2O. In each case the catalyst contained, on a weightpercent basis, about 20% of water.

In each run about 200% of t-he theoretical requirement of free-oxygenwas used-*in the form of commercial cylinder oxygen. The dispersion wasagitated for a time suicient Ito obtain a doctor sweet nap-htha. Thesweet naphtha was washed with 20 volume percent of water -at F. toremove occluded catalyst.

The oxidation stability of the sweet naphtha was determined by theinduction period method ASTM D525- 49. Prior to each oxidation testN,Ndisecbutylp phenylene diamine, l lb./M bbl. (42) and N,Ndisalicylidined,Z-diaminopropane, 2 lbs./ M bbl. (42), were added to theysweet cracked naphtha.

The results of these tests are shown below in the table.

TABLE Clay: CuCl2 Tempera- Induction Test No. Wt. Ratio ture, F. Period,

1Min.

Test 7 A sour virgin naphtha boiling between about `and 350 F. with amercaptan number of about 12 was sweetened under the conditions of Testl, except that no inhibitor and no metal deactivator was added. Thesweet naphtha had an induction period of 1400 minutes.

'I'histest shows that the problem of stability of copper chloridesweetened naphthas is limited to cracked naphthas.

The cracked naphtha that had been sweetened at 90 F. had a much betterSaybolt color than did the naphtha sweetened at F.

The data in the table must be considered in the light of therequirements of commerce. It is generally accepted that a gasoline. ofsatisfactory commercial storage stability must have an induction periodof at least 270 minutes. Better quality commercial gasolines haveinduction periods of about 400 minutes or more. These data clearly showthat the conventional sweetening process does not produce an acceptableproduct, whereas the process of this invention is substantially equal tobetter quality commercial gasoline.

Thus having described the invention, what is claimed 1. A process forsweetening a sour cracked naphtha, which process comprises dispersing ina sour cracked naphtha an effective amount of a granular catalystconsisting of cupric chloride, water and a carrier, wherein the watercontent is between about 15 and 25 weight percent of the catalyst andthe weight ratio of carrier to cupric chloride is between about 12:1 and15:1, at a temperature between about 70 F. and about 90 F. in thepresence of an amount of free oxygen sufficient to convert essentiallyall the mercaptans in said sour naphtha and thereby produce anessentially sweet naphtha,

maintaining said dispersion for a time sufcient to render said naphthaessentially sweet, separating essentially sweet naphtha from saidcatalyst and adding to said sweet naphtha a phenylene diamine inhibitorand a copper metal deactivator in an amount between about 0.5 and 5 lbs.per 1000 bbls. (42 gals.) of sweet naphtha respectively, whereby aproduct sweet naphtha is produced which is characterized by an inductionperiod of at least about 400 minutes.

2. The process of claim 1 wherein said sour naphtha is a thermallycracked naphtha.

3. The process of claim 1 wherein said phenylene diamine inhibitor isN,Ndisecbutylp-phenylene diamine.

4. The process of claim 1 wherein said deactivator isN,Ndisalicy1idine1,2-diaminopropane.

References Cited in the le of this patent UNITED STATES PATENTS OTHERREFERENCES Oil and Gas Journal, pages 107 and 108, December 14,

1. A PROCESS FOR SWEETENING A SOUR CRACKED NAPHTHA, WHICH PROCESSCOMPRISES DISPERSING IN A SOUR CRACKED NAPHTHA AN EFFECTIVE AMOUNT OF AGRANULAR CATALYST CONSISTING OF CUPRIC CHLORIDE, WATER AND A CARRIER,WHEREIN THE WATER CONTENT IS BETWEEN ABOUT 15 AND 25 WEIGHT PERCENT OFTHE CATALYST AND THE WEIGHT RATION OF CARRIER TO CUPRIC CHLORIDE ISBETWEEN ABOUT 12:1 AND 15:1, AT A TEMPERATURE BETWEN ABOUT 70* F. ANDABOUT 90* F. IN THE PRESENCE OF AN AMOUNT OF FREE OXYGEN SUFFICIENT TOCONVERT ESSENTIALLY ALL THE MERCAPTANS IN SAID SOUR NAPHTHA AND THEREBYPRODUCE AN ESSENTIALLY SWEET NAPHTHA, MAINTAINING SAID DISPERSION FOR ATIME SUFFICIENT TO RENDER SAID NAPHTHA ESSENTIALLY SWEET, SEPARATINGESSENTIALLY